noun

• (military) An area of hostile territory that has been seized for use as an airbase to ensure the further safe landing of troops and materiel.
  "The only difference between an airhead and a beachhead is that an airhead covers 360 degrees whereas a beachhead usually covers 180 degrees. An airhead is two beachheads back to back with the reinforcements and resupply coming by air instead of by sea. [...] [T]o handle their mountainous proportions there must be in the airhead a sufficient number of trained and equipped airhead service troops."
• (by extension) A (usually temporary) landing area for aircraft for supplying a non-military operation.
• (mining, archaic) Alternative form of air-head (“a horizontal channel providing ventilation in a mine.”).
  "[T]he mine then becomes exposed to the most fearful results, where the workings have been opened, by the Air being driven backwards along the Airhead into the reservoirs of Gas formed in the upper cavities of the workings, and issuing into the Gate-road charged with the Gas to the firing point, causing an explosion, of which many familiar instances might be adduced."

noun

• (originally US, informal, derogatory) A foolish, silly, or unintelligent person.
  "Sometimes people tell you directly that you aren't very smart, but most of the time they ignore your attempts to display your intelligence, or they kid you about being a "space case" or an "airhead." After a while you are bound to see yourself as not very intelligent, particularly if the people who have been sending you those messages about yourself are important to you."